The present invention relates to an inner wall protection member used to protect the inner wall of a chamber of a plasma processing apparatus, such as a plasma etching apparatus and a plasma CVD apparatus, for processing a silicon wafer in the fabrication of semiconductor devices such as ICs and LSIs, and to a plasma processing apparatus provided with the protection member.
A plasma processing apparatus used for plasma etching has upper and lower electrodes placed in a plasma processing chamber so as to face each other at a predetermined interval. Plasma is generated by discharging a reactive gas such as CF4, CHF3, Ar, and O2 from orifices in the upper electrode and applying high-frequency electric power to the lower and upper electrodes. A silicon wafer or the like is placed on the lower electrode and is etched utilizing the plasma.
As a material for the electrodes, aluminum, graphite, glass-like carbon, silicon, and the like are used. As a material for the inner wall of the plasma processing chamber, aluminum, alumina in which the surface of aluminum is oxidized, and the like are used.
The inner wall of the plasma processing chamber is chemically eroded and generates dust, whereby the inner wall is worn out. The dust adheres to the surface of the wafer and this results in a defective wafer, thereby decreasing the yield. Moreover, the chamber tends to be damaged earlier. To deal with this problem, a protection member is provided on the inner wall of the plasma processing chamber to prevent the inner wall from being worn out due to plasma.
Japanese Patent Application Laid-open No. 9-275092 discloses a plasma processing apparatus having a chamber in which a substrate to be processed is installed, a pump used to exhaust the inside of the chamber, electrodes for generating plasma using processing gas introduced into the chamber thereby irradiating the plasma to the substrate, a replaceable protection wall provided along the inner wall of the chamber with a predetermined opening therebetween, and a cooling means for introducing cooling gas into the opening to prevent the temperature of the surface of the protection wall from increasing due to heat generated in the chamber.
The Japanese Patent Application Laid-open No. 9-275092 relates to a structure for cooling the protection wall provided in the chamber of the plasma processing apparatus, wherein the protection wall is caused to absorb polymers represented by CxFy produced during plasma formation, thereby preventing the polymer from adhering to other areas of the chamber. Since this protection wall is easily replaced, the processing chamber can be efficiently cleaned. Moreover, since the increase in the temperature due to plasma of the surface of the protection wall can be prevented, stable processing is achieved.
Japanese Patent Application Laid-open No. 9-289198 discloses a plasma processing apparatus with a plasma processing chamber having electrodes for generating plasma, wherein at least the surface of the plasma processing chamber is formed of glass-like carbon in the area exposed to plasma excluding the electrodes. The Japanese Patent Application Laid-open No. 9-289198 also discloses a protection member for a plasma processing apparatus which is arranged in a plasma processing chamber provided with two electrodes for generating plasma, in which a plasma region is formed between the electrodes. The protection member is arranged so as to cover the plasma region between the electrodes, and at least the surface thereof facing the plasma region is formed of glass-like carbon.
According to the Japanese Patent Application Laid-open No. 9-289198, since the surface of the plasma processing chamber is formed of glass-like carbon in the area exposed to plasma, corrosion and wear due to plasma can be reduced. Moreover, the chamber can be used for a longer period of time due to low generation of particles (dust). Furthermore, contamination of the product to be processed due to dust can be prevented.
However, since plasma resistance of glass-like carbon materials varies depending on the properties thereof, such materials must be appropriately selected to obtain suitable performance as an inner wall protection member.
The present inventors have connected extensive studies on the properties of glass-like carbon materials suitably used for an inner wall protection member used to protect the inner wall of a chamber of a plasma processing apparatus. As a result, the present inventors have found that the glass-like carbon materials exhibit superior plasma resistance, generate only a small amount of dust, and are capable of generating and maintaining stable plasma. This finding has led to the completion of the present invention.
Specifically, an object of the present invention is to provide an inner wall protection member used to protect the inner wall of a chamber of a plasma processing apparatus which can be used in a stable manner over a long period of time, by specifying the properties of glass-like carbon materials, and a plasma processing apparatus provided with the protection member.
The inner wall protection member according to the present invention has a hollow structure and is integrally formed of glass-like carbon materials having a volume resistivity of 1xc3x9710xe2x88x922 xcexa9xc2x7cm or less and a thermal conductivity of 5 W/mxc2x7K or more. The protection member preferably has a thickness of 4 mm or more and the inner surface thereof preferably has an average surface roughness (Ra) of 2.0 xcexcm or less. The hollow structure used herein includes a cylindrical shape and a cylindrical shape with a hole or groove formed therein. In addition, the hollow structure includes a hollow prism in addition to a cylindrical shape.
The plasma processing apparatus according to the present invention has a chamber and a hollow inner wall protection member integrally formed of glass-like carbon materials having a volume resistivity of 1xc3x9710xe2x88x922 Qxc2x7cm or less and a thermal conductivity of 5 W/mxc2x7K or more, of which the thickness is preferably 4 mm or more and the inner surface has average surface roughness (Ra) of preferably 2.0 xcexcm or less, wherein the inner wall of the chamber and the protection member are electrically connected and the chamber is grounded.